linux-kernel - Re: [22/27] VFS: Fix automount for negative autofs dentries

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Date:	Sun, 23 Oct 2011 19:59:18 +0800
From:	Ian Kent <raven@...maw.net>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Greg KH <gregkh@...e.de>, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org, stable-review@...r.kernel.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	David Howells <dhowells@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Chuck Ebbert <cebbert@...hat.com>,
	Miklos Szeredi <miklos@...redi.hu>,
	Trond Myklebust <Trond.Myklebust@...app.com>
Subject: Re: [22/27] VFS: Fix automount for negative autofs dentries

On Sun, 2011-10-23 at 10:35 +0300, Linus Torvalds wrote:
> This one is debatable.
> 
> I think it also wants

Mmm .. I find myself caught by essentially the same mistake twice in one
day, ;)

> 
>  - commit 0ec26fd0698285b31248e34bf1abb022c00f23d6 (with
> LOOKUP_PARENT->LOOKUP_CONTINUE too)

Oh right "vfs: automount should ignore LOOKUP_FOLLOW", yes.

> 
>  - commit d94c177beeb4469cd4f6e83354ab0223353e98ed (to get the few
> other cases right too)

And probably 815d405ceff0d6964683f033e18b9b23a88fba87 as well as
b6c8069d3577481390b3f24a8434ad72a3235594. But I'd need to check that
would be OK.

That should bring 3.0 inline with 3.1.
	
> 
> anything else I missed?
> 
>              Linus
> 
> On Sun, Oct 23, 2011 at 9:24 AM, Greg KH <gregkh@...e.de> wrote:
> > 3.0-stable review patch.  If anyone has any objections, please let us know.
> >
> > ------------------
> >
> > From: David Howells <dhowells@...hat.com>
> >
> > commit 5a30d8a2b8ddd5102c440c7e5a7c8e1fd729c818 upstream.
> > [ backport for 3.0.x: LOOKUP_PARENT => LOOKUP_CONTINUE by Chuck Ebbert
> > <cebbert@...hat.com> ]
> >
> > Autofs may set the DCACHE_NEED_AUTOMOUNT flag on negative dentries.  These
> > need attention from the automounter daemon regardless of the LOOKUP_FOLLOW flag.
> >
> > Signed-off-by: David Howells <dhowells@...hat.com>
> > Acked-by: Ian Kent <raven@...maw.net>
> > Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
> > Cc: Chuck Ebbert <cebbert@...hat.com>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
> >
> > ---
> >  fs/namei.c |   24 +++++++++++++++---------
> >  1 file changed, 15 insertions(+), 9 deletions(-)
> >
> > --- a/fs/namei.c
> > +++ b/fs/namei.c
> > @@ -779,19 +779,25 @@ static int follow_automount(struct path
> >        if ((flags & LOOKUP_NO_AUTOMOUNT) && !(flags & LOOKUP_CONTINUE))
> >                return -EISDIR; /* we actually want to stop here */
> >
> > -       /* We want to mount if someone is trying to open/create a file of any
> > -        * type under the mountpoint, wants to traverse through the mountpoint
> > -        * or wants to open the mounted directory.
> > -        *
> > +       /*
> >         * We don't want to mount if someone's just doing a stat and they've
> >         * set AT_SYMLINK_NOFOLLOW - unless they're stat'ing a directory and
> >         * appended a '/' to the name.
> >         */
> > -       if (!(flags & LOOKUP_FOLLOW) &&
> > -           !(flags & (LOOKUP_CONTINUE | LOOKUP_DIRECTORY |
> > -                      LOOKUP_OPEN | LOOKUP_CREATE)))
> > -               return -EISDIR;
> > -
> > +       if (!(flags & LOOKUP_FOLLOW)) {
> > +               /* We do, however, want to mount if someone wants to open or
> > +                * create a file of any type under the mountpoint, wants to
> > +                * traverse through the mountpoint or wants to open the mounted
> > +                * directory.
> > +                * Also, autofs may mark negative dentries as being automount
> > +                * points.  These will need the attentions of the daemon to
> > +                * instantiate them before they can be used.
> > +                */
> > +               if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
> > +                            LOOKUP_OPEN | LOOKUP_CREATE)) &&
> > +                   path->dentry->d_inode)
> > +                       return -EISDIR;
> > +       }
> >        current->total_link_count++;
> >        if (current->total_link_count >= 40)
> >                return -ELOOP;
> >
> >
> >


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